Abstract: A digital switching matrix for use in telephone systems which provides non-blocking operation and is capable of non-blocking expansion without reconfiguration of the existing system. A provision for providing message tones such as dial tone, business line, etc., without requiring a map search of the switching matrix, and an integral testing provision are also described.

Abstract: A frame synchronization system for time division multiplexed data wherein all the time slots of the frame are considered during the course of the frame as opposed to being considered individually.The framing system comprises a first memory, e.g., a random access memory (RAM), and a second memory, e.g., a programmable read-only memory (ROM). The RAM includes respective locations corresponding to each relative bit time slot in the framing interval. The ROM includes respective locations corresponding to each correlation state in a predetermined sequence of states, respectively indicative of the number sequential bits in a given time slot matching the synchronization pattern. Each word in the ROM contains, in a link field, indicia of the ROM locations corresponding to the next state in the sequence. The ROM word also contains indicia of whether or not a correlation state has been attained indicative of the frame sync bit. Each RAM location is sequentially addressed in synchronism with the data input stream.

Abstract: A pulse code modulation, time division multiplex conferencing system for providing to each party channel a signal indicative of the linear sum of the samples from all other party-channels, such signals are generated by accumulating the sum of all samples from all party-channels, then generating an output signal to a particular party channel by subtracting from the sum the contribution of the particular party-channel. The cumulative sum is updated upon receipt of each new sample. Provisions for conferencing channels in a plurality of sequentially aligned frames are also disclosed.